The research aims to characterize how human beings perceive the intensity of odorants and irritants under various conditions of stimulation. The project focuses on a) the relative contributions of the olfactory and common chemical systems to odor magnitude and irritation, b) the efficacy of odor counteractants and masking agents, c) the resolution of small differences in odor intensity, and d) adaptation. Experiments will explore the perceived magnitude of mixtures containing an irritant and a non-irritating odorant. A question of primary interest is whether the irritant will mask odor. Experiments on intensity resolution will explore the ability of a gas-chromatograph to predict psychophysical performance and will attempt to relate differences in discriminability among odorants to differences in the rate of growth of the psychophysical function, i.e., the function that relates perceived magnitude to concentration. Experiments on odor counteraction will seek to devise a standardized procedure to assess the efficacy of putative counteractants. BIBLIOGRAPHIC REFERENCES: Cain, W.S. Differential sensitivity for smell: "Noise" at the nose. Science, 1977, 195, 796-798. Cain, W.S. Olfaction and the common chemical sense: Some psychophysical contrasts. Sensory Processes, 1976, 1, 57-67.